As known to those skilled in the art, the term “Internet” refers to the vast collection of computers and network devices that use various protocols to communicate with one another. A “client” computer connected to the Internet can download digital information from “server” computers connected to the Internet. Client application software executing on client computers typically accept commands from a user and obtain data and services by sending requests to server applications running on server computers connected to the Internet. A number of protocols are used to exchange commands and data between computers connected to the Internet. The protocols include the File Transfer Protocol (FTP), the Hypertext Transfer Protocol (HTTP), the Simple Mail Transfer Protocol (SMTP), and the “Gopher” document protocol.
The HTTP protocol is used to access data on the World Wide Web, often referred to as “the Web.” The World Wide Web is an information service on the Internet providing documents and links between documents. The World Wide Web is made up of numerous Web sites located around the world that maintain and distribute electronic documents. A Web site may use one or more Web server computers that store and distribute documents in one of a number of formats including the Hypertext Markup Language (HTML). An HTML document contains text and metadata such as commands providing formatting information. HTML documents also include embedded “links” that reference other data or documents located on any Web server computer. The referenced documents may represent text, graphics, or video in respective formats.
A Web browser is a client application or operating system utility that communicates with server computers via FTP, HTTP, and Gopher protocols. Web browsers receive electronic documents from the network and present them to a user. Internet Explorer, available from Microsoft Corporation, Redmond, Wash., is an example of a popular Web browser application.
In a network computing environment, as described above, some computer systems are configured to maintain a number of duplicated databases stored on a server computer (a Web server), and a plurality of client computers. For example, Web servers that transmit a substantial amount of data to client computers utilize database designs configured to store application data on a client computer as well as on the Web server. This duplicated database configuration allows client computers to perform certain operations without having to establish a network connection with a particular Web server. The distributed database configuration is also well-suited for client computers that are connected to a network through a slow data connection or via temporary connections such as a remote telephone connection.
One illustrative example of a computer system that is configured to maintain a number of duplicated databases stored on a plurality of client computers can be found at a financial Web site, such as one provided by Microsoft Corporation at the Web address, MONEYCENTRAL.MSN.COM. The Web server for the MoneyCentral Web site utilizes a duplicated database configuration where at least two client computers share a database with common data. This configuration allows a client computer to perform certain operations using the information stored on the client computer database without having to establish a network connection to the Web server while still allowing multiple client computers to share the database through a Web server.
The above-described duplicated database configuration presents some difficulties. Because of the nature of the mobility of users on large networks, such as the Internet, it is likely that one user may use more than one client computer to access a Web server. This may cause version control errors in the synchronization of duplicated databases because one client computer database may be different from a second client computer database. More specifically, when a particular client computer attempts to synchronize its database with the Web server, it is difficult for the Web server to determine if the client computer contains the most recent database. For example, if a user accesses a Web server from a client computer located at their office and another client computer located at their home, the Web server may not correctly update the Web server database if data is changed at both client computers. In this scenario, it is difficult to maintain and identify the duplicated databases stored in the client computers. In addition, it becomes increasingly difficult to identify the most recent information in client computer databases when the data of the Web server database is simultaneously changed by more than one client computer.
Accordingly, there is a need for a method and system for efficiently managing and synchronizing a plurality of duplicate databases stored on a server computer and more than one client computer. There is also a need for a method and system that identifies the most recent database between a plurality of duplicate client computer databases that may be simultaneously accessing a server computer database.